1. Technical Field of the Invention
The present invention relates to a sunlight collection apparatus for gathering sunlight from outdoors and guiding the sunlight by means of optical fiber cables to shine inside greenhouses for plant cultivation or inside residences.
2. Related Art
In recent years, various types of sunlight collection apparatuses for gathering sunlight, i.e. natural light, and guiding the light to shine inside greenhouses for plant cultivation or inside residences. This type of sunlight collection apparatus usually comprises a light condenser section for gathering sunlight from outdoors to a single area, a light conducting section for guiding the sunlight gathered at the light collection section, and a light scattering section for irregularly reflecting the sunlight guided by the light conducting section indoors. Conventional sunlight collection apparatuses can be largely divided into (1) types which use ducts as the light conducting means and (2) types which use optical fiber cables as the light conducting means.
Sunlight collection apparatuses which use ducts for the light conducting section as in type (1) mentioned above have a structure wherein sunlight is received at the entrance portion of a duct by means of reflection, the received sunlight is guided to the required room by reflecting the light along the duct, and the room is lit by the sunlight by means of irregular reflection at the light scattering section.
Sunlight collection apparatuses which use optical fiber cables for the light conducting section as in type (2) mentioned above have a structure wherein a lens element having a solar tracking device focuses sunlight at the focal point of the lens element while tracking the sun, the sunlight is guided to the required room through an optical fiber cable having one end surface positioned at the focal point of the lens element, and the room is lit by the sunlight by means of a light scattering material provided at the other end of the optical fiber cable.
However, the above-mentioned conventional sunlight collection apparatuses have the following problems. With regard to type (1), the installation work can be complicated because the light conducting section is formed from ducts, so that a portion of the building must be destroyed in order to install the apparatus in a building which is already standing, thus greatly increasing the cost and inflating the price of installation.
With regard to type (2), the light conducting section is able to be easily installed in buildings because the light conducting section is formed from optical fiber cables, but the light collection section has a large lens element and a tracking device for tracking the sun, so that the support structures for holding the lens element and the tracking device must be complicated, thereby greatly increasing the cost and making the price too high for general purposes.
Additionally, with regard those types which track the sun, the structure must be such as to position the end surface of the optical fiber cable of the light conducting section at the focal point of a large-diameter lens element and continually track the sun in order to maintain the sun on the optical axis of the lens element so that the sunlight can be gathered and received at the focal point on the end surface of the optical fiber cable. Therefore, the tracking device is extremely costly and requires extreme precision to track the sun.